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The recent outbreak of Legionnaire’s pneumonia in Flint Michigan and its link in time and space to metal contamination of the public water supply (lead and iron) teaches us, once again, that we live in an interconnected environment. Change one thing and multiple consequences can accrue.
The complex chain of cause and effect, as we are learning from the unfolding Michigan debacle, can include both toxic pollutants and infectious agents. This point was brought home to me by a completely unrelated report that surfaced just a public attention was being drawn north to the Great Lakes State (one of whose other nicknames is the “Water Wonderland”). It turns out that farther to the West, another outbreak has been occurring. In December, the Centers for Disease Control (CDC) reported that a different human disease was on the upswing. Called tularemia, this infection can be every bit as dangerous as Legionella, and then some (http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6447a4.htm). “Upswing,” in fact, may understate the trend. Compared to the 10 years prior to calendar year 2015, the number of cases of tularemia being reported in Colorado, Nebraska, South Dakota and Wyoming was up 975%, 200%, 186% and 700%, respectively. The hundred cases in total subsumed by this outbreak are roughly on the scale of the Legionella surge in and around Flint.
Tularemia is a bacterial infection that humans pick up from the environment: it can cause pneumonia, swollen glands, and also a general illness marked by fever and pain (not reassuringly, this is referred to as a “typhoidal” form of the disease). It doesn’t take much exposure, either. Indeed, this infectious agent has been considered a potential bioterror threat precisely because of its virulence. In its report on the multi-state tularemia outbreak, the CDC was cautious to note that its cause was unclear and that possible factors included “increased rainfall promoting vegetation growth, pathogen survival, and increased rodent and rabbit populations.”
Exposure to rabbits, in particular, has long been known to be an important potential tularemia exposure scenario especially among hunters, giving the disease one of its common monikers: “rabbit fever.” Just over half of the new outbreak cases reported an animal contact of some sort. An additional one third reported insect bites - historically, deer fly bites have been another well recognized vector of transmission. But what was really noteworthy among the 100 new cases was that 49 of them reported “environmental aerosolizing activities.” One assumes this must have been put in other words by the patients themselves. Examples the CDC gives for sources of “aerosolization” include “landscaping, mowing over voles, hares or rodents, or other farming activities.”
The brevity of this laundry list of outdoor aerosol no-no’s was reassuring. After all, most of us don’t mow over voles routinely. Still, I was intrigued by the vague reference to “landscaping.” Did this mean manning an earthmover or simply piddling in the garden? A little digging of my own led me to research that had been carried out on an outbreak of tularemia-caused pneumonia on Martha’s Vineyard back in the year 2000. Epidemiological investigation showed that professional landscapers there were 32 times more likely than others on the island to come down with the infection. This observation spurred on the same investigative team to do a follow-up study, this time targeting landscapers in detail in order to tease out specific work-related risk factors that accounted for their exposure. The single most potent activity leading to infection was use of a power blower (http://www.ncbi.nlm.nih.gov/pubmed/12643831).
Ever since its relatively recent introduction, the motor-powered leaf blower had served as something of lightning rod. Although rarely in the literal sense, as in the case of a 38 year old Floridian reportedly struck when he climbed up on his roof leaf-blower in hand (http://articles.sun-sentinel.com/2000-07-16/news/0007160241_1_roof-ligh…), leaf blowers largely have galvanized opposition largely because of air pollution and noise. A 2000 “Report to the California Legislature on the Potential Health and Environmental Impacts of Leaf Blowers” emphasized these issues, for example, but mentioned not a word on the potential spread of infection (http://www.arb.ca.gov/msprog/mailouts/msc0005/msc0005.pdf).
Ten years later, a New Yorker profile on “the great suburban leaf war” updated the controversy, but tularemia remained unmentioned, apparently lost in the noise that is the most obvious leaf blower bone of contention (http://www.newyorker.com/magazine/2010/10/25/blowback). The Martha’s Vineyard epidemic was a decade old by that point. But the risk of infection in landscapers has not gone away. The 2009 case of a 21-year old in New Mexico who came down with life-threatening meningitis from tularemia underscores this (http://www.ncbi.nlm.nih.gov/pubmed/19364939). His doctors at first were puzzled by the illness: “He had recently changed jobs and did not initially report that he had worked as a professional landscaper until 7 days before the onset of symptoms. He had performed lawn mowing and leaf blowing services and noted the he had seen dead rabbits in the areas in which he worked.”
Of course, tularemia can occur in Michigan, too, as its State Department of Natural Resources warns, listing infected animals to include the muskrat, beaver, cottontail rabbit and snowshoe hare (http://www.michigan.gov/dnr/0,4570,7-153-10370_12150_12220-27293--,00.h…). State image makers may be relieved that at least the wolverine does not appear to be a carrier.
